Power tools and other portable electrical equipment are generally equipped with a relatively short electrical power cord having a male plug at the end thereof. However, a longer power cord is often required to provide power to the tools in an area remotely located from an electrical outlet. As a result, power tools are frequently connected to remote outlets via extension cords. An extension cord is an electric cord fitted with a male plug at one end and a female receptacle at the other end. The female receptacle end of the extension cord is mated with the male plug of the power tool cord. The male plug of the extension cord is inserted into a conventional outlet, providing an electrical connection between the outlet and the power tool. Additionally, numerous extension cords may be connected together, extending the distance of the electrical connection between power tools and remote outlets.
Electrical cords maintain a plugged together relationship between prongs of the male plug and corresponding receptacles of the female plug through friction. The friction between the plugs is adequate to maintain the electrical cords in a plugged together relationship when the cords are stationary. However, the friction between plugs may be insufficient to hold the electrical cords together when the cords are moved around, such as at a construction site. In the latter situation, the insufficient friction between the plugs causes them to accidentally separate, interrupting the flow of electricity to the power tool. The interruption of the flow of electricity to the tool can be annoying and time consuming, and sometimes possibly dangerous in certain situations.
Numerous inventions have been devised to solve the problem of accidental separation of the male and female plugs of electrical cords. One solution has been the use of a device that clamps the male and female plugs together. A device that clamps plugs together is disclosed in U.S. Pat. No. 4,183,603, issued to Carmo. The Carmo patent shows various mechanisms for holding the connection between the plugs, including, for example, a thumbwheel which is rotated to firmly press the male plug and the female plug together. Another device that holds the connection between plugs is disclosed in U.S. Pat. No. 3,383,639, issued to Anderson et al. The Anderson patent shows an extension cord coupling clamp conforming around the ends of the male and female plugs to keep them connected. These devices, however, place an undue amount of strain on the connection between the plugs, and, therefore, may damage the plugs or the electrical cords.
Accordingly, some devices have been constructed to relieve, at least partially, the strain on the connection by clamping the electrical cords without imposing unnecessary forces on the plugs themselves. For example, a strain relief device having a pair of clamps connected by a threaded rod extension is disclosed in U.S. Pat. No. 3,609,638, issued to Darrey. Each clamp securely grips the electrical cord with the connected male and female ends disposed therebetween. Such devices which employ a clamp or similar apparatus may damage the electrical integrity of the conductors, the insulation, or the cover of the extension cord.
Other strain relief devices have been constructed without the use of potentially damaging clamps. In U.S. Pat. No. 5,255,866, issued to Campolo, a stain relief device is disclosed consisting of a rigid hollow cylinder with two rigid flanges extending at opposite ends of the cylinder. The joined plugs of two electrical cords are positioned inside the cylinder. Each respective cord is bent back through slots in the flanges and wound around the cylinder between the flanges, thereby transmitting tension between the electrical cords to the cylinder and flanges. However, these devices waste a considerable amount of the extension cord due to the necessity of winding the cord around the device to transfer the strain from the cord to the device. In addition, devices such as the one disclosed by Campolo prevents visual inspection of the connection between the two cords.
Therefore, it is an object of this invention to provide a device with a practical construction for maintaining the connection between male and female plugs while not imposing undue strain on the plugs.
Another object of this invention is to provide a device for holding the connection between male and female plugs and which can be manufactured easily and at a low cost from commercially available materials.
A further object of this invention is to provide a device for maintaining the connection between male and female plugs and which prevents the cords from becoming worn or damaged.
Yet another object of this invention is to provide a device for holding the connection between male and female plugs and which the user can easily inspect the integrity of the connection between the male and female plugs.
These and other objects and advantages of the present invention will become apparent from the following description.